I don't think you want to orient the cooler with the input and output at the bottom.
Our last update concluded with a startling revelation: Our LS-swapped 350Z’s oil temperatures were skyrocketing on track. Thanks to The Sensor Connection, we quickly saw that just two mild laps were enough to send our oil to 260 degrees–and higher. Without fixing something, we risked damaging our V8.
Clearly, we needed an oil cooler.
How does an oil cooler work? Well, they work just like any other heat exchanger–like a radiator, a/c condenser or transmission cooler.
Oil coolers are just pipes with a high surface area to volume ratio, meaning they’re good at transferring heat from the fluid running through them to the air flowing over them.
How do you choose an oil cooler? For an application like this, the decision tree is easy: Find something the right size and shape, built well, with an efficient design.
For a race car, that will almost always mean a stack plate cooler.
There are two common types of heat exchangers: stack plate and tube-and-fin.
Tube-and-fin coolers are exactly as they sound: It’s a round tube covered in fins. These certainly dissipate more heat than a plain hose, but they’re not nearly as efficient as stacked plate coolers.
As the name suggests, these stack plate coolers are made with thin, wide tubes–smashed to look like plates, basically–that carry fluid from one end of the cooler to the other. These have more surface area for heat to transfer, and stack plate coolers are more efficient for the same size/weight than their tube and fin competition.
We’ve used Derale coolers in the past on other products and knew they were built well, reasonably priced, and offered in a variety of sizes.
So we measured the nose of our 350Z and settled on a 34-row stack plate cooler, part No. 53410. Summit Racing offers this part for $222.59, and it includes -10 AN fittings which should tie in nicely with our existing oil system.
Derale offers a pair of nicely made anodized aluminum mounting brackets with hardware for $57.79, so we added them to our order, too (part No. 50023). Everything we bolted onto our 350Z totaled about eight pounds.
We’d chosen our cooler. Now we needed to tie it into our existing oiling system.
Since our 350Z already runs a remote oil filter, it would have been easy to extend those lines and plumb the cooler directly into the existing system.
However, that would bring an unintended consequence we didn’t want: Oil that’s potentially too cold.
Oil doesn’t just hate being hot. It hates being cold, too, which is one reason it’s a good idea to warm your engine up before going on track. Flowing all of our oil through the cooler all the time would mean cold oil until we started hammering on the car on track, and that would mean extra wear and tear on our engine.
Just like your radiator coolant has a thermostat to help the engine warm up, so too can your oil cooler: Summit sells Derale fluid thermostats for $46.29, so we ordered one for our 350Z. This thermostat routes most oil around the cooler until it hits 180 degrees, when the thermostat closes and all oil is routed through the cooler.
Why not completely block the cooler when cold? Because doing so would cause a sudden shock when the thermostat opens. This design prevents a major pressure or temperature differential from building up while still preventing most heat transfer. Derale sells fittings, too, so we ordered another $50 worth of adapters (part No. 59310) to complete our oil thermostat installation.
Parts in hand, it was time for installation. Mounting the cooler was easy–we used riv-nuts to bolt it directly to the 350Z’s core support in front of the radiator, pairing one Derale bracket with two others we made ourselves.
Is this the perfect position for an oil cooler? Well… sort of. The upper half is partially blocked by the bumper, but it lines up perfectly with the radiator and the radiator fan. Especially once we add some ducting, we should have plenty of airflow through this cooler. We chose against mounting the cooler lower in order to protect it (and therefore our oiling system) from any off-track excursions.
We’d mounted the cooler, and now we needed to plumb it. After lots of time spent holding lines up to the car and staring at it, we settled on a plan: Suspend the thermostat in mid-air under the air filter, which would allow us to plumb the cooler with the least amount of additional hose and fittings.
Doing that would mean making a custom bracket, which we knocked out in a few hours thanks to the skills we’ve learned in our series on Making Stuff, including intricate brackets like the one now holding our oil thermostat.
After a bit more time making AN hoses, we stepped back to admire our work: Success!
Does it work?
Our oil cooler sure looked the part, but did it work? It was time to find out, so we loaded up the trailer and went to the Florida International Rally & Motorsports Park, the official test track of Grassroots Motorsports. Our mission was simple: Run laps until the car overheats its oil, hopefully staying out on track for at least three or four flyers.
Sadly, we never accomplished our mission–because the car refused to overheat! Even after back-to-back-to-back hot laps in 95-degree heat, the 350Z’s oil gauge rose to 240 degrees and stayed there. We didn’t even find any leaking fittings after a few sessions on track, so we’re going to call this a success.
For a total investment of about $500 including all line, fittings and hardware, we’d solved our 350Z’s oil temperature problem. Now that our 350Z will run back-to-back laps without issue, it’s time to keep making it faster. We’ll cover that in our next installment.
I don't think you want to orient the cooler with the input and output at the bottom.
I debated a few orientations, and settled on this one because it provided better airflow and easier hose routing. There are pros and cons to ports on the bottom, but in theory there is enough flow to push any bubbles out and it doesn't really matter.
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